1. Field of the Invention
The present invention relates to testing and calibration of radio equipment and modules.
2. Discussion of the Known Art
Manual, open loop methods of calibrating electrical circuits in radio frequency (RF) receivers, transmitters, modules, and other communications equipment are generally known. Such procedures include, e.g., setting tuned filter voltages or amplifier bias voltages by hand at different frequencies and temperatures.
Typically, an operator needs to measure and record a number of different parameters, determine whether or not the results obtained are within a desired range, and make incremental adjustments manually if needed in order to converge on a solution. Depending on the number of independent variables to be adjusted, it could take multiple iterations before the operator obtains the desired results. Repeating this procedure for many different frequencies, power levels and temperatures can therefore be very time consuming and costly.
U.S. Pat. No. 5,201,063 (Apr. 6, 1993), which is incorporated by reference, discloses an automated procedure for calibrating a radiotelephone. Computer controlled test equipment are connected to the device under test, and an output of the device is measured in response to inputs from the equipment. If an output for a given parameter under test is not within predetermined levels, an adjustment signal is produced and the output is monitored again. Further adjustments are made until the result is within a set limit, according to the patent. See also, U.S. Pat. No. 5,262,957 (Nov. 16, 1993) and No. 7,242,910 (Jul. 10, 2007), and U.S. Pat. Appl'n Pub. No. 2011/0216858 (Sep. 8, 2011), all of which are incorporated by reference.
Notwithstanding the known art, there is a need for a procedure that allows a number of different operating parameters of a communications unit under test to be measured and set within desired limits automatically, quickly, and with improved repeatability compared to the known calibration techniques. There is also a need for a procedure by which the parameters can be easily checked and adjusted periodically, in order to correct for drift over time.